A parent's worst nightmare would surely be that their much-loved child has been murdered by their other much-loved child. I don't think Ian over-acted, either. The absolute despair, depicted by pacing, arm-waving, and grimacing and wailing is just what might happen. Although we do keep in mind that this is a story and not real life, we see these reactions every day on the news when a parent has lost a child in a war situation. I think he did well.